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SubjectRe: 21 million inodes is causing severe pauses.
Robin Holt <holt@sgi.com> wrote:
>
> On Tue, Nov 16, 2004 at 11:13:21AM -0800, Andrew Morton wrote:
> > Robin Holt <holt@sgi.com> wrote:
> > >
> > > I guess I am very concerned at this point. If I can do a
> > > release/reacquire, why not just change generic_shutdown_super() so the
> > > lock_kernel() does not happen until the first pass has occurred. ie:
> > >
> > > --- super.c.orig 2004-11-16 10:22:17 -06:00
> > > +++ super.c 2004-11-16 10:22:41 -06:00
> > > @@ -232,10 +232,10 @@
> > > dput(root);
> > > fsync_super(sb);
> > > lock_super(sb);
> > > - lock_kernel();
> > > sb->s_flags &= ~MS_ACTIVE;
> > > /* bad name - it should be evict_inodes() */
> > > invalidate_inodes(sb);
> > > + lock_kernel();
> > >
> > > if (sop->write_super && sb->s_dirt)
> > > sop->write_super(sb);
> > >
> > > This at least makes the lock_kernel time much smaller than it is right
> > > now. It also does not affect any callers that may really need the BKL.
> >
> > lock_kernel() is also taken way up in do_umount(), hence the need for
> > release_kernel_lock()/reacquire_kernel_lock().
>
> It looks like it is only held very briefly during the early parts of do_umount.
>

OK.

> I have moved lock_kernel() as above in addition to the two patches you pointed
> to earlier. This has left me with a system which has 21M inodes and undetectable
> delays during heavy mount/umount activity. I am starting one last test which
> attempts a umount of a filesystem which has many inodes associated with it.

That sounds good. We need to work out where that null-pointer deref is
coming from.

> At this point, I have checked the entire code path and see no reason the
> BKL is held for the first call to invalidate_inodes.

No, the above change looks fine. And I have no problem merging up
invalidate_inodes-speedup.patch, really - it's been in -mm for over a year.
I've just been waiting for a decent reason to merge it.

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